Such devices are found in many fields, and more particularly in aviation, a field in which the problems associated with this type of device have been posed to the inventors.
Specifically, these devices are routinely used for controlling various functional portions of aircraft or helicopters, and particularly the automatic pilot control.
In this particular field, it is essential to ensure a permanent operating security of the electronic components of the device, in order to ensure the security and precision of the automatic pilot.
Some electronic devices designed for the automatic pilot control comprise, implemented on the supporting board, two distinct control electronic circuits capable of taking over from one another in the event of a failure.
Because of the extreme heat conditions to which the components are subjected, it is necessary to provide uninterrupted ventilation of the device. Usually, this ventilation is provided by a current of cooling air that flows parallel to the surface of the supporting board.
A disadvantage of this arrangement is that, when a component of one of the circuits explodes, the current of cooling air risks carrying the debris of the component in question and spreading it over the parallel circuit. Because of the sensitivity of certain components of the latter, the debris risks damaging the parallel circuit, not to mention that, if this debris is conductive, it may create short circuits in the parallel circuit.
In order to solve this problem, document FR 2 864 423 has proposed a device with integrated electronic components provided with a meshed separating partition. More precisely, document FR 2 864 423 proposes a device with integrated electronic components, that comprises a board forming a support for the components, and a cover mounted on the board to cover the components, and a meshed partition which extends from the cover to the board substantially perpendicularly to the latter, the partition separating two distinct zones of the board in which electronic components are placed.
More precisely, FIG. 1 represents a plan view of a board forming a support for the electronic circuits, and notably described in document FR 2 864 423, and FIG. 2 is a schematic view in perspective of the zone protection device described in this same document FR 2 864 423.
FIG. 2 also illustrates a device 1 with integrated electronic components 2, that comprises a board 3, represented in plan view in FIG. 1, forming a support on which the components 2 are implemented, and a cover 4 designed to be mounted on the board 3 to cover the components 2 and thereby protect them from the consequences of a possible destruction of some of them.
As can be seen in FIG. 1, the components 2 are grouped into two distinct adjacent zones 5, 6 which form two distinct control electronic circuits. These are in practice control circuits for an automatic pilot system of an aircraft or of a helicopter. In the rest of the description, these circuits are respectively called CHANNEL A and CHANNEL B.
As appears in FIG. 1, the channels A and B are slightly separated from one another, an interstice 7 being arranged between them on the board 3. The details of producing the circuits 5, 6 will not be described. Note however that the board 3 comprises a substantially rectangular plate 8 made of an insulating material that forms the support on which the components 2 are implemented.
Note also that the board 3 has a front edge 9 onto which are mounted a primary connector 10 for plugging in a test cable and debugging channel A and a secondary connector 11 adjacent to the primary connector 10 for plugging in a test cable and debugging channel B. The board 3 also has a rear edge 12, at the other end from the front edge 9, on which are mounted, on the side of channel A, a backplane primary connector 13 for plugging in a power supply bus and connecting channel A to the controlled system (in this instance, the automatic pilot) and, on the side of channel B, a secondary backplane connector 14 for plugging in a power supply bus and for connecting channel B to the controlled system.
As can be seen in FIG. 1, the board 3 has, on the side of its front edge 9, two auxiliary zones 15, 16 in which filtering capacitors 17, 18 are implemented associated with channels A and B respectively.
The board 3 may also comprise a partition 19 that separates the auxiliary zones 15, 16 of the respective channels A and B in order to isolate the capacitors 17, 18 from the other components 2 of the corresponding channel. According to a preferred embodiment, this partition consists of a front edge of the cover 4.
In addition, as can be seen in FIG. 2, the board 3 has, along two lateral edges 20, 21 joining the front edge 9 and rear edge 12, two walls 22, 23, namely an upstream wall 22 bordering channel B and a downstream wall 23 bordering, at the other end, channel A, walls in which openings 24 are made to allow a current of cooling air to pass through which, sweeping through the upstream wall 22 (arrows F1), is discharged through the downstream wall 23 (arrows F2) after having sustained a heat transfer with the components 2 of channels A and B. In this instance, the lateral partitions 22 and 23 are formed by radiators fixed to the board 3, which allow high calorific dissipation electronic components to be mounted on the latter. If such radiators are unnecessary, the lateral partitions 22, 23 could be formed by lateral edges of the cover 4.
The cover 4 for its part comprises a substantially flat bottom wall 25 of substantially rectangular shape, designed to jointly cover channels A and B and having a front edge 26 and a rear edge 27 designed to be placed in line with the front edge 9 and rear edge 12 of the board 3 respectively, connected by two parallel side edges 28, 29 designed to be placed between and against the upstream wall 22 and the downstream wall 23 of the board 3.
However, the Applicant has been able to ascertain that the device described in document FR 2 864 423 does not allow sufficient and equivalent ventilation and cooling of channels A and B of the board 3.
Specifically, before cooling channel A, the ventilation current has already passed through channel B. The air reaching the level of channel A has therefore already been heated and cannot cool channel A in an equivalent manner.
The object of the invention is in particular to solve this problem by producing a device allowing cooling that is identical between channel A and channel B of the board 3.
It is a known practice according to the prior art to provide in this case a double ventilation circuit, namely a ventilation circuit for channel A and a ventilation circuit for channel B. To do this, in order to allow the formation of two identical ventilations for the two channels A and B, it is necessary to provide a thermal channel passing through channel A and a thermal channel passing through channel B. This solution requires a vertical placement of channels A and B: for example, channel A in a front zone, and channel B in a rear zone. But then, if the idea of boards that can be plugged into a backplane is maintained, to retain the access of channel A to the backplane rear connectors, and where necessary the access of channel B to the front face test connectors, it becomes necessary to define, through each of the channels, a transit zone for the power supplies and signals of the opposite channel.
In addition, this solution is unsatisfactory in terms of cost and space requirement.
The object of the invention is therefore to solve the aforementioned disadvantages by proposing a device of the aforementioned type, which allows an identical or equivalent ventilation of two channels of a plug-in board by forming a thermal segregation of the two channels while preventing any thermal coupling between the two channels.
The aim of one of the subjects of the invention is also to avoid the failure of one circuit board leading to the failure of the other, and to guarantee an increased operating security of the electronic components.
The aim of one of the subjects of the invention is also to form a fire-preventive segregation, namely to form an electromagnetic interference shield between two identical channels of a plug-in board.